yaytt/dist/youtube-api.js

Blazingly fast YouTube caption extractor with deduplication.

export class YouTubeAPI {
    async getVideoInfo(videoId) {
        let apiKey;
        try {
            apiKey = await this.extractApiKey(videoId);
        }
        catch {
            apiKey = YouTubeAPI.FALLBACK_API_KEY;
        }
        const response = await fetch(`${YouTubeAPI.INNERTUBE_ENDPOINT}?key=${apiKey}`, {
            method: 'POST',
            headers: {
                'Content-Type': 'application/json',
                'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36',
                'Accept': '*/*',
                'Accept-Language': 'en-US,en;q=0.9',
                'Origin': 'https://www.youtube.com',
                'Referer': `https://www.youtube.com/watch?v=${videoId}`,
                'X-YouTube-Client-Name': '1',
                'X-YouTube-Client-Version': '2.20210721.00.00'
            },
            body: JSON.stringify({
                context: {
                    client: {
                        clientName: 'WEB',
                        clientVersion: '2.20210721.00.00'
                    }
                },
                videoId: videoId
            })
        });
        if (!response.ok) {
            throw new Error(`YouTube API request failed: ${response.status} ${response.statusText}`);
        }
        return await response.json();
    }
    async extractApiKey(videoId) {
        const videoPageResponse = await fetch(`https://www.youtube.com/watch?v=${videoId}`, {
            headers: {
                'User-Agent': YouTubeAPI.USER_AGENT
            }
        });
        if (!videoPageResponse.ok) {
            throw new Error('Failed to fetch video page');
        }
        const html = await videoPageResponse.text();
        const apiKeyMatch = html.match(/"INNERTUBE_API_KEY":"([^"]+)"/);
        if (!apiKeyMatch) {
            throw new Error('Could not extract API key from video page');
        }
        return apiKeyMatch[1];
    }
    async getCaptionTracks(videoId) {
        const playerResponse = await this.getVideoInfo(videoId);
        const captionTracks = playerResponse?.captions?.playerCaptionsTracklistRenderer?.captionTracks;
        if (!captionTracks || captionTracks.length === 0) {
            throw new Error(`No captions available for video: ${videoId}`);
        }
        return captionTracks;
    }
    async downloadCaptions(captionUrl) {
        const response = await fetch(`${captionUrl}&fmt=vtt`, {
            headers: {
                'User-Agent': YouTubeAPI.USER_AGENT,
                'Accept': '*/*',
                'Referer': 'https://www.youtube.com/'
            }
        });
        if (!response.ok) {
            throw new Error(`Failed to download captions: ${response.status} ${response.statusText}`);
        }
        return await response.text();
    }
    parseVTT(vttContent) {
        const lines = vttContent.split('\n');
        const cues = [];
        for (let i = 0; i < lines.length; i++) {
            const line = lines[i].trim();
            if (line.includes('-->')) {
                const timeMatch = line.match(/(\d{2}:\d{2}:\d{2}\.\d{3})\s*-->\s*(\d{2}:\d{2}:\d{2}\.\d{3})/);
                if (timeMatch) {
                    const startTime = this.parseTimestamp(timeMatch[1]);
                    const endTime = this.parseTimestamp(timeMatch[2]);
                    let text = '';
                    for (let j = i + 1; j < lines.length; j++) {
                        const textLine = lines[j].trim();
                        if (textLine === '') {
                            break;
                        }
                        if (text)
                            text += ' ';
                        text += this.cleanCaptionText(textLine);
                    }
                    if (text) {
                        cues.push({
                            start: startTime,
                            end: endTime,
                            text: text
                        });
                    }
                }
            }
        }
        return cues;
    }
    parseTimestamp(timestamp) {
        const parts = timestamp.split(':');
        const seconds = parts[2].split('.');
        const hours = parseInt(parts[0], 10);
        const minutes = parseInt(parts[1], 10);
        const secs = parseInt(seconds[0], 10);
        const milliseconds = parseInt(seconds[1], 10);
        return hours * 3600 + minutes * 60 + secs + milliseconds / 1000;
    }
    cleanCaptionText(text) {
        return text
            .replace(/<[^>]*>/g, '')
            .replace(/&amp;/g, '&')
            .replace(/&lt;/g, '<')
            .replace(/&gt;/g, '>')
            .replace(/&quot;/g, '"')
            .replace(/&#39;/g, "'")
            .trim();
    }
}
YouTubeAPI.INNERTUBE_ENDPOINT = 'https://www.youtube.com/youtubei/v1/player';
YouTubeAPI.FALLBACK_API_KEY = 'AIzaSyAO_FJ2SlqU8Q4STEHLGCilw_Y9_11qcW8';
YouTubeAPI.USER_AGENT = 'Mozilla/5.0 (Linux; Android 11; SM-G973F) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.120 Mobile Safari/537.36';